Bergenin (compound of formula II) is a dihydroisocoumarin derivative and is the main bioactive component of Saxifragaceae. In 1880, Garrean extracted the bergenin from the plant of the genus Huer, but did not complete its structural determination until 1958. Numerous studies have confirmed that bergenin has a variety of biological activities, including anti-cancer, anti-hepatotoxicity, anti-oxidation, anti-arrhythmia, anti-HIV and neuroprotective properties. In addition, studies have shown that bergenin has an anti-oxidative repair effect on tissue damage caused by 2,4-DNPH and alcoholism, and at the same time has a certain effect on eliminating the side effects of oxidants in blood and metabolism. Takahashi et al. (Takahashi H, Kosaka M, Watanabe Y, et al. Synthesis and neuroprotective activity of bergenin derivatives with antioxidant activity. Bioorganic & Medicinal Chemistry, 2003, 11(8): 1781-1788.) The bergenin was obtained from Davidia involucrata. It was found that bergenin has a good scavenging effect on DPPH free radicals and superoxide anions, and the antioxidant effect is remarkable. By modifying the sugar bond of bergenin by binding with various fatty acids, its antioxidant activity can be enhanced, indicating that the structural modification of bergenin provides the possibility of obtaining novel antioxidants.
Lipoic acid (LA) (compound of formula III), also known as α-lipoic acid (ALA), is a natural disulfide compound that was first isolated from pig liver by Reed in 1951. It is one of B vitamins. As a natural antioxidant, lipoic acid is a water-soluble and fat-soluble amphiphilic molecule. Both oxidized and reduced forms have strong antioxidant effects in both water and lipid environments. In addition, lipoic acid can exert anti-tumor effects by inhibiting tumor angiogenesis, enhancing immunity, increasing tumor sensitivity to chemotherapeutic drugs, and reversing tumor resistance, so lipoic acid has high medical value and anti-aging potential.
In the present invention, 11-hydroxyl group of bergenin is dehydrated and condensed with lipoic acid carboxyl group to form an ester bond, thereby obtaining a bergenin lipoic acid ester. Preliminary antioxidant experiments show that the compound has excellent antioxidant activity and has high medical research and application value in the field of antioxidant health products.